According to Stephen Farthing, instructor at the Univ. of Arts in London, (reported in the wsj) the average time a gallery visitor spends in front of a painting is no more than two or three seconds.

As I so often speak about when delivering my speeches, the majority of web visitors spend only few seconds on your home page. These visitors would only spend more time if you successfully and quickly grabbed their attention with points of interest and valuable content and products.